It is well-known in the field of cardiology that ventricular tachyarrhythmias can be effectively treated by the application of electrical shocks to the heart. Such defibrillation may be achieved by the application of electrical paddles to the chest of the patient or directly to the heart tissue, if the chest is open during surgery.
More recent improvements have lead to the development of implantable defibrillators, which monitor the heart for arrhythmias an automatically initiate defibrillation when a tachyarrhythmia occurs. Such devices often incorporate electrodes that are located on the epicardium or parietal pericardium, being connected to a defibrillation unit by means of a lead.
However, major surgery is generally necessary to implant and affix present defibrillator lead systems into their desired position. For example, a median sternotomy or lateral thoracotomy may be required. Such procedures can be very traumatic to the patient, and may have adverse side effects such as surgical complications. Because of the significant surgical risks of the present lead systems, many patients who might otherwise benefit from the use of an implantable defibrillator are excluded from using one.
The issue of fixation of leads in a desired position in the body can be important for any implantable device, but it is especially important for defibrillator leads, since to prevent a short circuit, the electrodes of the typical pair of defibrillator leads cannot be allowed to come into close proximity to each other. When implanting paddle electrodes via conventional thoracotomy or sternotomy, there is adequate access to the leads and surrounding tissues to secure the leads with suture to those tissues in order to fixate their position. However, in the case of a paddle electrode placed through a small incision using a limited surgery technique, or a deployable lead that has been placed through a small aperture, suturing by hand is not possible due to the lack of access. A deployable lead is one that can be inserted into the body in a collapsed configuration, and later be expandable to a new configuration, which has dimensions that are larger than the incision which provided entry of the lead into the body.
Another difficulty involved in fixating leads to the epicardium, when compared to fixating leads to the endocardium, relates to the lack of trabeculae for engagement with tines, and also the presence of coronary blood vessels that must be avoided if one attempts to use screw or hooks that penetrate the tissue.
By this invention, a lead is preferably attached to the pericardium, and not the epicardial surface of the heart, thus decreasing the likelihood of complications such as coronary vessel damage, myocardial laceration or excessive hemorrhage. The described tool allows the positioning of the lead to its desired location on the pericardium, the grasping of pericardial tissue, withdrawing the pericardium away from the underlying heart and then the safe delivery of a fastener, which attaches and fixates the lead to the previously grasped tissue. The fastener may be attached firmly, yet relatively atraumatically, since only fibrous tissue is grasped and penetrated. One possible fastener device is one that has no sharp edges exposed to tissue once it has been applied. The grasping jaws may be an integral component of the tool, or the tool may provide a hollow lumen for delivery of different grasping tools, which could then be used in conjunction with the fastening tool. The tool may also incorporate a small fiber optic scope for visualization of the procedure.
Thus, the invention of this application exhibits significant advantages over prior art methods for implanting defibrillation leads, particularly adjacent the heart, as shown in Chin et al. U.S. Pat. No. 4,865,037 or Person U.S. Pat. No. 3,999,555, for example. It also exhibits significant advantages over existing surgical clip appliers (Ethicon, U.S. Surgical) by allowing a fastener to be placed safely on one tissue without risk of piercing or damaging an underlying structure.
Other objects and advantages of the present invention will become apparent as the description proceeds.